1. Field of the Invention
The present invention relates to an IDTV (Improved Definition television) set.
2. Description of Background Information
IDTV represents a television set adapted for receiving a video signal of the present television broadcast standard, and improving the quality of picture only on the set's side by a signal processing operation using a field memory or a frame memory. Such IDTV sets are now being introduced in the market.
An example of the structure of the IDTV set is shown in FIG. 1. As shown in this figure, a composite video signal inputted through a video input terminal 1 is supplied to a motion adaptive Y/C separation circuit 2 and to a motion sensing circuit 3. The motion adaptive Y/C separation circuit 2 is, for example, configured to perform an inter-line Y/C separation operation, and an inter-frame Y/C separation operation, and to determine the ratio between the inter-line Y/C separation and the inter-frame Y/C separation in accordance with a detection output signal of the motion sensing circuit 3. More specifically, the inter-frame Y/C separation operation becomes dominant in the motion adapted Y/C separation circuit 2 when the pictures being treated is close to a still picture, and the inter-line Y/C separation operation becomes dominant when the picture being treated contains a lot of motions. By this feature, the Y/C separation operation without generating the cross color and the cross luminance disturbances can be attained for still pictures, and also the Y/C separation operation without generating the so called blur can be attained for motion pictures (pictures having motion).
The luminance signal and color signals separated in the motion adaptive Y/C separation circuit 2 are supplied to a chroma demodulation and matrix circuit 4, in which three primary color signals of R(red), G(greeen), B(blue) are generated by a matrix composition of signals obtained after a chroma demodulation operation. These three primary colors are supplied to a motion adaptive scanning line converting circuit 5. In the motion adaptive scanning line coverting circuit 5, the RGB signals having 525/2 lines/field and which is an interlace signal having the ratio of 2:1 are converted to R'G'B' signals having a double line density of 525 lines/field, and the R'G'B' signals are in turn supplied to a CRT 6. The motion adaptive scanning line converting circuit 5 is controlled by the detection output signal of the motion sensing circuit 3. In short, an interpolating operation is performed when the number of the scanning lines is converted from (525/2) lines/field to 525 lines/field. Moreover, the field interpolating operation is performed for still pictures containing no motion, and the line interpolating operation is performed within the present frame in the case of motion pictures. By this feature, non-interlaced scanning is performed, so that the line flickering is eliminated, the vertical resolution is improved, and the blur of motion is eliminated.
As described above, by inputting a composite color video signal to an IDTV set, it becomes possible to enjoy images which are not suffering from the cross color and cross luminance disturbances and the line flickering, while having an improved vertical resolution. Moreover, pictures without the time-wise blur can be obtained.
However, conventional IDTV sets are constructed to receive a composite video signal, so that it was not possible to directly use luminance and chrominance signals outputted from a device having separate terminals for Y and C signals, such as VTRs (video tape recorders), or VCRs. For this reason, there has been a restriction that the input signal must be in the form of a composite video signal. Thus, it was not possible to make the most of once completely separated luminance and chrominance signals.